Highly active double metal cyanide complex catalysts

ABSTRACT

Improved double metal cyanide catalysts are disclosed. The substantially amorphous catalysts of the invention are more active for polymerizing epoxides than conventional DMC catalysts, which have a substantial crystalline component. Polyol products made with the catalysts are unusually clear, have exceptionally low unsaturations, and contain no detectable amount of low molecular weight polyol impurities. Methods of making the improved DMC catalysts are also disclosed. In one method, the reactants are intimately combined to produce a catalyst of the invention. In another method, an organic complexing agent is initially present in the reactant solutions.

FIELD OF THE INVENTION

The invention relates to double metal cyanide (DMC) complex catalystcompositions. The catalysts are highly active in epoxidepolymerizations. The invention includes improved methods for preparingthe compositions. Polyether polyol products made using the catalystcompositions have exceptionally low unsaturations.

BACKGROUND OF THE INVENTION

Double metal cyanide complex compounds are well known catalysts forepoxide polymerization. The catalysts are highly active, and givepolyether polyols that have low unsaturation compared with similarpolyols made using basic (KOH) catalysis. Conventional DMC catalysts areprepared by reacting aqueous solutions of metal salts and metal cyanidesalts to form a precipitate of the DMC compound. The catalysts can beused to make a variety of polymer products, including polyether,polyester, and polyetherester polyols. Many of the polyols are useful invarious polyurethane coatings, elastomers, sealants, foams, andadhesives.

Conventional DMC catalysts are usually prepared in the presence of a lowmolecular weight complexing agent, typically an ether such as glyme(dimethoxyethane) or diglyme. The ether complexes with the DMC compound,and favorably impacts the activity of the catalyst for epoxidepolymerization. In one conventional preparation, aqueous solutions ofzinc chloride (excess) and potassium hexacyanocobaltate are combined bysimple mixing. The resulting precipitate of zinc hexacyanocobaltate isthen mixed with aqueous glyme. An active catalyst is obtained that hasthe formula:

Zn₃ Co(CN)₆ !₂.xZnCl₂.yH₂ O.zGlyme

Other known complexing agents include alcohols, ketones, esters, amides,ureas, and the like. (See, for example, U.S. Pat. Nos. 3,427,256,3,427,334, 3,278,459, and Japanese Pat. Appl. Kokai Nos. 4-145123,3-281529 and 3-149222). Generally, the catalyst made with glyme has beenthe catalyst of choice. The catalysts have relatively high surfaceareas, typically within the range of about 50-200 m² /g.

Normally, the complexing agent is added to the reaction mixturefollowing precipitation of the DMC compound. Some references, such asU.S. Pat. No. 5,158,922, indicate that the complexing agent can beincluded with either or both of the aqueous reactant solutions, but noreference teaches any particular advantage of having the complexingagent present in the reactant solutions.

Double metal cyanide compounds prepared in the absence of a complexingagent are highly crystalline by X-ray diffraction analysis (See FIG. 4),and are inactive for epoxide polymerization. When the complexing agentsdescribed above are used, the resulting catalysts actively polymerizeepoxides. Our X-ray diffraction analyses of active DMC complexesprepared according to methods known in the art suggest that conventionalDMC catalysts are actually mixtures of a highly crystalline DMC compoundand a more amorphous component. Typically, conventional DMCcatalysts--which are generally prepared by simple mixing--contain atleast about 35 wt. % of highly crystalline DMC compound. DMC compoundsuseful as epoxide polymerization catalysts and containing less thanabout 30 wt. % of highly crystalline DMC compound are not known.

Double metal cyanide catalysts generally have good activity for epoxidepolymerizations, often much greater than conventional basic catalysts.However, because the DMC catalysts are rather expensive, catalysts withimproved activity are desirable because reduced catalyst levels could beused.

Double metal cyanide catalysts normally require an "induction" period.In contrast to basic catalysts, DMC catalysts ordinarily will not beginpolymerizing epoxides immediately following exposure of epoxide andstarter polyol to the catalyst. Instead, the catalyst needs to beactivated with a small proportion of epoxide before it becomes safe tobegin continuously adding the remaining epoxide. Induction periods of anhour or more are typical yet costly in terms of increased cycle times ina polyol production facility. Reduction or elimination of the inductionperiod is desirable.

An advantage of DMC catalysts is that they permit the synthesis of highmolecular weight polyether polyols having relatively low unsaturation.The adverse impact of polyol unsaturation on polyurethane properties iswell documented. (See, for example, C. P. Smith et al., J. Elast.Plast., 24 (1992) 306, and R. L. Mascioli, SPI Proceedings, 32nd AnnualPolyurethane Tech./Market. Conf. (1989) 139.) When a DMC catalyst isused, polyols having unsaturations as low as about 0.015 meq/g can bemade. Polyether polyols with even lower unsaturations can be made if asolvent such as tetrahydrofuran is used to make the polyol. See, forexample, U.S. Pat. Nos. 3,829,505 and 4,843,054. However, for commercialpolyol production, the use of a solvent is not particularly desirable.Thus, other ways to further reduce polyol unsaturation are needed.

When conventional DMC catalysts are used to polymerize epoxides, thepolyether polyol products contain relatively low levels (about 5-10 wt.%) of low molecular weight polyol impurities. A way to eliminate thesepolyol impurities is desirable because improved polyurethanes couldresult from the use of more monodisperse polyols.

Double metal cyanide complex catalyst residues are often difficult toremove from polyether polyols, and a wide variety of methods have beendeveloped to cope with the problem. Removal of DMC catalyst residuesfrom the polyols promotes long-term storage stability and consistentpolyol performance in urethane formulation. Most methods involve somekind of chemical treatment of the polyol following polymerization. Therehas been little progress made in developing catalyst preparation methodsthat ultimately facilitate catalyst removal from the polyol products.

SUMMARY OF THE INVENTION

The invention is an improved catalyst for polymerizing epoxides. We havesurprisingly found that substantially amorphous DMC complexes are muchmore active than conventional DMC complexes for epoxide polymerization.In addition, the amorphous complexes are more quickly activated (showreduced induction periods) compared with conventional DMC catalysts.

The catalysts of the invention comprise at least about 70 wt. % of asubstantially amorphous DMC complex; more preferred compositionscomprise from about 90-99 wt. % of the substantially amorphous DMCcomplex. The more preferred compositions exhibit a powder x-raydiffraction pattern having substantially no sharp lines at about 5.1(d-spacings, angstroms).

The invention also includes compositions which comprise thesubstantially amorphous DMC complexes described above, and up to about30 wt. % of a highly crystalline DMC compound; more preferredcompositions contain less than about 1 wt. % of the highly crystallineDMC compound.

The invention includes methods for preparing the improved catalysts.Although conventional methods for making DMC complex catalysts have beenknown for about 30 years, no one has previously appreciated that themethod of combining the reactants is extremely important. We have nowdiscovered, quite surprisingly, that the way of combining the reactants,and particularly the way in which the organic complexing agent isintroduced into the DMC complex, is extremely important. One way to makethe highly active, substantially amorphous DMC complexes of theinvention is to intimately combine the reactants during preparation byhomogenization or high-shear mixing. Aqueous solutions of awater-soluble metal salt and a water-soluble metal cyanide salt areintimately combined in the presence of a complexing agent to produce anaqueous mixture containing the DMC complex catalyst. The catalyst, whichis then isolated and dried, comprises at least about 70 wt. % of asubstantially amorphous DMC complex.

In a second method, the organic complexing agent, preferably tert-butylalcohol, is added to one or both of the aqueous reactant solutionsbefore they are combined to produce the DMC complex. This method avoidsthe need to intimately combine the reactants by homogenization orhigh-shear mixing.

The invention also includes a method for preparing an epoxide polymer.The method comprises polymerizing an epoxide in the presence of acatalyst which comprises at least about 70 wt. % of a substantiallyamorphous DMC complex.

The invention also includes polyether polyol compositions that areuniquely available from using the catalysts of the invention. Thepolyols have exceptionally low unsaturations and contain unusually lowlevels of low molecular weight polyol impurities.

Finally, the invention includes a method for improving the filterabilityof a DMC complex catalyst from a polyether polyol product followingepoxide polymerization. The method comprises using, as a polymerizationcatalyst, a substantially amorphous DMC complex catalyst of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plot of propylene oxide consumption versus time during apolymerization reaction with one of the catalyst compositions of theinvention at 250 ppm catalyst. The induction time for the run ismeasured as discussed in Example 6 from the intersection of the extendedbaseline and slope measurements.

FIGS. 2-10 are powder x-ray diffraction patterns of various double metalcyanide compounds. These are described more fully below.

DETAILED DESCRIPTION OF THE INVENTION

The catalysts of the invention, unlike conventional DMC compounds knownin the art as useful for epoxide polymerization, comprise at least about70 wt. % of a substantially amorphous DMC complex. More preferredcatalysts of the invention comprise at least about 90 wt. % of asubstantially amorphous DMC complex; most preferred are catalystscomprising at least about 99 wt. % of a substantially amorphous DMCcomplex.

As defined in this application, "substantially amorphous" meanssubstantially noncrystalline, lacking a well-defined crystal structure,or characterized by the substantial absence of sharp lines in the X-raydiffraction pattern of the composition. Powder X-ray diffraction (XRD)patterns of conventional double metal cyanide catalysts showcharacteristic sharp lines that correspond to the presence of asubstantial proportion of a highly crystalline DMC component (see FIGS.2 and 3). Highly crystalline zinc hexacyanocobaltate prepared in theabsence of an organic complexing agent, which does not activelypolymerize epoxides, shows a characteristic XRD fingerprint of sharplines at d-spacings of about 5.07, 3.59, 2.54, and 2.28 angstroms (seeFIG. 4).

When a DMC catalyst is made in the presence of an organic complexingagent according to conventional methods, the XRD pattern shows lines forthe highly crystalline material in addition to broader signals fromrelatively amorphous material, suggesting that conventional DMCepoxidation catalysts are actually mixtures of highly crystalline DMCcompound and a more amorphous component (see FIG. 3). Typically,conventional DMC catalysts, which are generally prepared by simplemixing, contain at least about 35 wt. % of highly crystalline DMCcompound.

The catalysts of the invention are distinguishable from conventional DMCcompositions based on their substantial lack of crystalline material.The substantial lack of crystallinity is evidenced by an XRD patternshowing that little or no highly crystalline DMC compound is present.When a zinc hexacyanocobaltate catalyst is prepared according to themethod of the invention using tert-butyl alcohol as a complexing agent,for example, the X-ray diffraction pattern shows essentially no linesfor crystalline zinc hexacyanocobaltate (5.07, 3.59, 2.54, 2.28angstroms), but instead has only two major lines, both relatively broad,at d-spacings of about 4.82 and 3.76 angstroms (see FIG. 5). A similarpattern is observed when the method of the invention is used with glymeas a complexing agent (see FIG. 6).

Spiking experiments demonstrate that DMC catalysts prepared by themethod of the invention typically contain less than about 1 wt. % ofhighly crystalline DMC compound. (See FIG. 7, which shows that even 1wt. % of highly crystalline DMC compound can be detected by X-rayanalysis when spiked into a sample of a substantially amorphous catalystof the invention). FIG. 8 shows a mixture that contains a substantiallyamorphous DMC catalyst spiked with 5 wt. % of highly crystalline DMCcompound. FIG. 9 shows a mixture that contains a substantially amorphousDMC catalyst spiked with 25 wt. % of highly crystalline DMC compound.(Such a catalyst falls within the scope of the invention, which containsat least 70 wt. % of a substantially amorphous DMC catalyst.) Finally,FIG. 10 shows that the X-ray pattern for a substantially amorphouscatalyst of the invention, when spiked with 40 wt. % of highlycrystalline DMC compound, closely resembles the pattern observed for aDMC catalyst made by a conventional catalyst preparation. Some of theX-ray results are summarized in Table 1.

Conventional DMC catalysts typically contain at least about 35 wt. % ofhighly crystalline DMC compound. No one has previously recognized thedesirability of preparing substantially amorphous catalysts, and thepotential value of reducing the content of highly crystalline DMCcompounds in these catalysts. It appears, based on our results, that thehighly crystalline DMC compound acts as either a diluent or as a poisonfor the more active amorphous form of the catalyst, and its presence ispreferably minimized or eliminated.

The invention includes compositions which comprise at least about 70 wt.% of the substantially amorphous DMC complex catalysts of the inventionand up to about 30 wt. % of a highly crystalline DMC compound. Morepreferred compositions of the invention comprise at least about 90 wt. %of the substantially amorphous DMC complex catalyst and up to about 10wt. % of the highly crystalline DMC compound. Most preferred arecompositions that contain at least about 99 wt. % of the substantiallyamorphous DMC complex catalyst and up to about 1 wt. % of the highlycrystalline material.

The catalyst compositions of the invention have relatively low surfaceareas. Conventional DMC compounds have surface areas within the range ofabout 50 to about 200 m² /g. In contrast, the surface areas of thecatalysts of the invention are preferably less than about 30 m² /g. Morepreferred compositions have surface areas less than about 20 m² /g.

Double metal cyanide compounds useful in the invention are the reactionproducts of a water-soluble metal salt and a water-soluble metal cyanidesalt. The water-soluble metal salt preferably has the general formulaM(X)_(n) in which M is selected from the group consisting of Zn(II),Fe(II), Ni(II), Mn(II), Co(II), Sn(II), Pb(II), Fe(III), Mo(IV), Mo(VI),Al(III), V(V), V(IV), Sr(II), W(IV), W(VI), Cu(II), and Cr(III). Morepreferably, M is selected from the group consisting of Zn(II), Fe(II),Co(II), and Ni(II). In the formula, X is preferably an anion selectedfrom the group consisting of halide, hydroxide, sulfate, carbonate,cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate, carboxylate,and nitrate. The value of n is from 1 to 3 and satisfies the valencystate of M. Examples of suitable metal salts include, but are notlimited to, zinc chloride, zinc bromide, zinc acetate, zincacetonylacetate, zinc benzoate, zinc nitrate, iron(II) sulfate, iron(II)bromide, cobalt(II) chloride, cobalt(II) thiocyanate, nickel(II)formate, nickel(II) nitrate, and the like, and mixtures thereof.

The water-soluble metal cyanide salts used to make the double metalcyanide compounds useful in the invention preferably have the generalformula (Y)_(a) M'(CN)_(b) (A)_(c) in which M' is selected from thegroup consisting of Fe(II), Fe(III), Co(II), Co(III), Cr(II), Cr(III),Mn(II), Mn(III), Ir(III), Ni(II), Rh(III), Ru(II), V(IV), and V(V). Morepreferably, M' is selected from the group consisting of Co(II), Co(III),Fe(II), Fe(III), Cr(III), Ir(III), and Ni(II). The water-soluble metalcyanide salt can contain one or more of these metals. In the formula, Yis an alkali metal ion or alkaline earth metal ion. A is an anionselected from the group consisting of halide, hydroxide, sulfate,carbonate, cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate,carboxy late, and nitrate. Both a and b are integers greater than orequal to 1; the sum of the charges of a, b, and c balances the charge ofM'. Suitable water-soluble metal cyanide salts include, but are notlimited to, potassium hexacyanocobaltate(III), potassiumhexacyanoferrate(II), potassium hexacyanoferrate(III), calciumhexacyanocobaltate(III), lithium hexacyanoiridate(III), and the like.

Examples of double metal cyanide compounds that can be used in theinvention include, for example, zinc hexacyanocobaltate(III), zinchexacyanoferrate(III), zinc hexacyanoferrate(II), nickel(II)hexacyanoferrate(II), cobalt(II) hexacyanocobaltate(III), and the like.Further examples of suitable double metal cyanide compounds are listedin U.S. Pat. No. 5,158,922, the teachings of which are incorporatedherein by reference.

The catalyst compositions of the invention are prepared in the presenceof a complexing agent. Generally, the complexing agent must berelatively soluble in water. Suitable complexing agents are thosecommonly known in the art, as taught, for example, in U.S. Pat. No.5,158,922. The complexing agent is added either during preparation orimmediately following precipitation of the catalyst. As is explainedelsewhere in this application, the manner in which the complexing agentis introduced into the DMC complex can be extremely important. Usually,an excess amount of the complexing agent is used. Preferred complexingagents are water-soluble heteroatom-containing organic compounds thatcan complex with the double metal cyanide compound. Suitable complexingagents include, but are not limited to, alcohols, aldehydes, ketones,ethers, esters, amides, ureas, nitriles, sulfides, and mixtures thereof.Preferred complexing agents are water-soluble aliphatic alcoholsselected from the group consisting of ethanol, isopropyl alcohol,n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butylalcohol. Tert-butyl alcohol is most preferred.

The conventional method of preparing DMC compounds useful for epoxidepolymerization is fully described in many references, including U.S.Pat. Nos. 5,158,922, 4,843,054, 4,477,589, 3,427,335, 3,427,334,3,427,256, 3,278,457, and 3,941,849, and Japanese Pat. Appl. Kokai No.4-145123. The teachings of these references related to conventionalcatalyst preparation and suitable DMC compounds are incorporated hereinby reference in their entirety.

The invention includes methods for making substantially amorphous DMCcatalyst compositions of the invention. One method comprises two steps.First, aqueous solutions of a water-soluble metal salt and awater-soluble metal cyanide salt (the "reactant solutions") areintimately combined and reacted in the presence of a complexing agent toproduce an aqueous mixture that contains a precipitated DMC complexcatalyst. Second, the catalyst is isolated and dried. The complexingagent can be included with either or both of the aqueous salt solutions,or it can be added to the DMC compound immediately followingprecipitation of the catalyst. It is preferred to pre-mix the complexingagent with either the water-soluble metal cyanide salt, or with thewater-soluble metal salt, or both, before intimately combining thereactants. The resulting catalyst composition is substantiallyamorphous, as is evidenced by the substantial absence of highlycrystalline DMC compound by X-ray diffraction analysis.

We surprisingly discovered that achieving an intimate combination of thereactants is important for preparing catalysts having low crystallinity.In conventional methods, the water-soluble metal salt and thewater-soluble metal cyanide salt are combined in aqueous media and aresimply mixed together, typically with magnetic or mechanical stirring.The organic complexing agent is then added. This method of preparationresults in catalysts having a substantial amount of highly crystallineDMC component, typically greater than about 35 wt. %. We found thatcombining the reactants in a manner effective to achieve an intimatecombination of the reactants results in substantially amorphouscatalysts that are exceptionally useful for epoxide polymerization.Suitable methods of achieving this intimate combination of reactantsinclude homogenization, impingement mixing, high-shear stirring, and thelike. When the reactants are homogenized, for example, the amount ofhighly crystalline material in the catalyst composition is minimized oreliminated, and is much lower than the amount of highly crystallinematerial present in a catalyst made by simple mixing. Examples 1 and 2show how to make a catalyst by the first method.

A second method of the invention is also effective in producing asubstantially amorphous DMC complex. In this method, the organiccomplexing agent is added to one or both of the aqueous reactantsolutions before they are combined to produce the DMC complex. Thismethod guarantees that the complexing agent will be available during theformation of the DMC compound. Preferably, the organic complexing agentis tert-butyl alcohol. Although the reactant solutions can be intimatelycombined by homogenization or high-shear mixing as described above, wefound that this method gives a substantially amorphous DMC complex ofthe invention without the need for intense mixing of the reactants.Examples 8-11 show how to make a catalyst of the invention by the secondmethod.

To summarize, substantially amorphous DMC catalysts of the invention canbe made by two general methods. In one method, the reactant solutionsare intimately combined by homogenization, high-shear mixing, or thelike. Intimate combination is needed if the organic complexing agent isadded following precipitation of the DMC compound. A second method ofmaking substantially amorphous DMC catalysts avoids the need forintimate combination of the reactants. In this method, the complexingagent is present in one or both of the reactant solutions before theyare combined to produce the DMC compound.

With either of the two methods of the invention described above, theorder of addition of reagents (metal salt solution to metal cyanide saltsolution, or vice versa) is not critical. Either method gives asubstantially amorphous DMC compound with either order of addition ofthe reactants.

We surprisingly found, however, that when the second method is used(i.e., when the organic complexing agent is present in one or both ofthe reactant solutions before they are combined), a much more activecatalyst results if the metal cyanide salt solution is added to themetal salt solution. See Examples 13-14 below. Thus, when the secondmethod of preparing the catalyst is used, it is preferred to add themetal cyanide salt solution to the metal salt solution.

The invention includes a process for making an epoxide polymer. Thisprocess comprises polymerizing an epoxide in the presence of a doublemetal cyanide catalyst composition of the invention. Preferred epoxidesare ethylene oxide, propylene oxide, butene oxides, styrene oxide, andthe like, and mixtures thereof. The process can be used to make randomor block copolymers. The epoxide polymer can be, for example, apolyether polyol derived from the polymerization of an epoxide in thepresence of a hydroxyl group-containing initiator.

Other monomers that will copolymerize with an epoxide in the presence ofa DMC compound can be included in the process of the invention to makeother types of epoxide polymers. Any of the copolymers known in the artmade using conventional DMC catalysts can be made with the catalysts ofthe invention. For example, epoxides copolymerize with oxetanes (astaught in U.S. Pat. Nos. 3,278,457 and 3,404,109) to give polyethers, orwith anhydrides (as taught in U.S. Pat. Nos. 5,145,883 and 3,538,043) togive polyester or polyetherester polyols. The preparation of polyether,polyester, and polyetherester polyols using double metal cyanidecatalysts is fully described, for example, in U.S. Pat. Nos. 5,223,583,5,145,883, 4,472,560, 3,941,849, 3,900,518, 3,538,043, 3,404,109,3,278,458, 3,278,457, and in J. L. Schuchardt and S. D. Harper, SPIProceedings, 32nd Annual Polyurethane Tech./Market. Conf. (1989) 360.The teachings of these U.S. patents related to polyol synthesis usingDMC catalysts are incorporated herein by reference in their entirety.

The substantially amorphous DMC catalysts of the invention are highlyactive compared to conventional DMC catalysts (see Table 2). Forexample, a zinc hexacyanocobaltate catalyst made using tert-butylalcohol as a complexing agent and made by homogenization (and containingless than 1 wt. % of crystalline DMC compound by X-ray analysis) isabout 65% more active at 100 ppm, and 200% more active at 130-250 ppm,than the same catalyst made by simple mixing (and containing about 35wt. % crystalline DMC compound). A consequence of higher polymerizationrates is that polyol producers can use less of the relatively expensiveDMC catalyst and save money. More active catalysts also permit theproducer to reduce batch times and increase productivity.

The substantially amorphous catalyst compositions of the invention showa reduced induction period compared with conventional catalysts in apolyether polyol synthesis (see Table 3). Conventional DMC catalysts arenot immediately active toward epoxide polymerization. Typically, astarter polyol, the catalyst, and a small amount of epoxide are combinedand heated to the desired reaction temperature, and no epoxidepolymerizes immediately. The polyol manufacturer must wait (often forseveral hours) until the catalyst becomes active and the charged epoxidebegins to react before additional epoxide can safely be continuouslyadded to the polymerization reactor. The substantially amorphouscatalysts of the invention are more rapidly activated than conventionalcatalysts that contain up to 35 wt. % of crystalline DMC compound. Thisfeature of the catalysts is also an economic advantage because delays inadding the epoxide are reduced.

Polyether polyols prepared using the catalysts of the invention haveexceptionally low unsaturations, consistently less than about 0.007meq/g. These unsaturations are at least about 50% lower than polyolunsaturations available from the DMC catalysts previously known (seeTable 4). Preferred polyols of the invention have unsaturations lessthan about 0.006 meq/g, and more preferably less than about 0.005 meq/g.The reduction in unsaturation compared with polyols previously availablefrom conventional DMC catalysts should offer some advantages forpolyurethanes made with the polyols of the invention.

Polyether polyols made with the catalysts of the invention preferablyhave average hydroxyl functionalities from about 2 to 8, more preferablyfrom about 2 to 6, and most preferably from about 2 to 3. The polyolspreferably have number average molecular weights within the range ofabout 500 to about 50,000. A more preferred range is from about 1,000 toabout 12,000; most preferred is the range from about 2,000 to about8,000.

Polyols prepared with the catalysts of the invention also havesubstantially lower levels of low molecular weight polyol impuritiescompared with polyols prepared with conventional catalysts. Gelpermeation chromatography (GPC) analysis of these polyols shows nodetectable low molecular weight polyol impurities. In contrast,conventional DMC catalysts made in the usual way with glyme as acomplexing agent show a marked GPC peak corresponding to about 5-10 wt.% of a low molecular weight polyol impurity.

Interestingly, polyols made with the catalysts of the invention areusually clearer than polyols made with conventional glyme catalysts; theformer typically remain clear even after weeks of storage at roomtemperature, while the latter tend to quickly develop a haze duringstorage.

Another advantage of the substantially amorphous catalysts of theinvention is that they are more easily removed from polyether polyolsfollowing polyol synthesis compared with conventional DMC compounds. Theproblem of how to remove DMC compounds from polyether polyols has beenthe subject of many investigations (see, for example, U.S. Pat. Nos.5,144,093, 5,099,075, 5,010,047, 4,987,271, 4,877,906, 4,721,818, and4,355,188). Most of these methods irreversibly deactivate the catalyst.

The catalysts of the invention can be isolated by simply filtering thepolyol. Another way to isolate the catalyst is to first dilute thepolyol with a solvent such as heptane to reduce viscosity, then filterthe mixture to recover the catalyst, and then strip the polyol/heptanemixture to obtain the purified polyol. The methods described in U.S.Pat. No. 5,010,047 can also be used to recover the catalysts of theinvention from polyols. An advantage of the catalysts of the inventionis that they can be removed cleanly from polyols even with a hotfiltration in the absence of any solvent. In contrast, when a polyolmade with a conventional glyme catalyst is hot-filtered, substantialamounts of the DMC compound remain in the polyol. If desired, theisolated catalyst composition of the invention can be recovered andreused to catalyze another epoxide polymerization reaction because thesesimple filtration methods do not generally deactivate the catalysts.

The following examples merely illustrate the invention. Those skilled inthe art will recognize many variations that are within the spirit of theinvention and scope of the claims.

EXAMPLE 1 Preparation of Zinc Hexacyanocobaltate Catalysts byHomogenization Tert-butyl Alcohol as the Complexing Agent (Catalyst D)

Potassium hexacyanocobaltate (8.0 g) is added to deionized water (150mL) in a beaker, and the mixture is blended with a homogenizer until thesolids dissolve. In a second beaker, zinc chloride (20 g) is dissolvedin deionized water (30 mL). The aqueous zinc chloride solution iscombined with the solution of the cobalt salt using a homogenizer tointimately mix the solutions. Immediately after combining the solutions,a mixture of ted-butyl alcohol (100 mL) and deionized water (100 mL) isadded slowly to the suspension of zinc hexacyanocobaltate, and themixture is homogenized for 10 min. The solids are isolated bycentrifugation, and are then homogenized for 10 min. with 250 mL of a70/30 (v:v) mixture of tert-butyl alcohol and deionized water. Thesolids are again isolated by centrifugation, and are finally homogenizedfor 10 min with 250 mL of tert-butyl alcohol. The catalyst is isolatedby centrifugation, and is dried in a vacuum oven at 50° C. and 30 in.(Hg) to constant weight. This catalyst is identified as Catalyst D, andhas the powder X-ray diffraction pattern shown in FIG. 5.

EXAMPLE 2

Preparation of Zinc Hexacyanocobaltate Catalysts by HomogenizationIsopropyl Alcohol as the Complexing Agent (Catalyst E)

The procedure of Example 1 is modified as follows. Isopropyl alcohol issubstituted for tert-butyl alcohol. Following combination of the zincchloride and potassium hexacyanocobaltate solutions and homogenizationin the presence of isopropyl alcohol, the catalyst slurry is filteredthrough a 0.45 micron filter at 20 psi. The washing steps of Example 1are also repeated, but filtration rather than centrifugation is used toisolate the catalyst. The washed catalyst is dried to constant weight asdescribed above. The catalyst is identified as Catalyst E.

COMPARATIVE EXAMPLE 3 Preparation of Zinc Hexacyanocobaltate Catalystsby Simple Mixing Tert-butyl Alcohol as the Complexing Agent (Catalyst B)

The procedure of Japanese Pat. Appl. Kokai No. 4-145123 is generallyfollowed. Potassium hexacyanocobaltate (4.0 g) is added to deionizedwater (75 mL) in a beaker, and the mixture is stirred until the solidsdissolve. In a second beaker, zinc chloride (10 g) is dissolved indeionized water (15 mL). The aqueous zinc chloride solution is combinedwith the solution of the cobalt salt using a magnetic stirring bar tomix the solutions. Immediately after combining the solutions, a mixtureof tert-butyl alcohol (50 mL) and deionized water (50 mL) is addedslowly to the suspension of zinc hexacyanocobaltate, and the mixture isstirred for 10 min. The solids are isolated by centrifugation, and arethen stirred for 10 min. with 100 mL of a 70/30 (v:v) mixture oftert-butyl alcohol and deionized water. The solids are again isolated bycentrifugation, and are finally stirred for 10 min with 100 mL oftert-butyl alcohol. The catalyst is isolated by centrifugation, and isdried in a vacuum oven at 50° C. and 30 in. (Hg) to constant weight.This catalyst is identified as Catalyst B, and has the powder X-raydiffraction pattern shown in FIG. 3.

COMPARATIVE EXAMPLE 4 Preparation of Zinc Hexacyanocobaltate Catalystsby Simple Mixing Isopropyl Alcohol as the Complexing Agent (Catalyst C)

The procedure of Comparative Example 3 is followed, except thatisopropyl alcohol is used in place of tert-butyl alcohol, and the solidsare isolated by filtration using a 0.8 micron filter rather than bycentrifugation. The catalyst is isolated and dried as described above.This catalyst is identified as Catalyst C.

COMPARATIVE EXAMPLE 5 Preparation of Crystalline Zinc HexacyanocobaltateNo Complexing Agent (Catalyst A)

Potassium hexacyanocobaltate (4.0 g) is dissolved in deionized water(150 mL) in a beaker. Zinc chloride (10 g) is dissolved in deionizedwater (15 mL) in a second beaker. The aqueous solutions are quicklycombined and magnetically stirred for 10 min. The precipitated solidsare isolated by centrifugation. The solids are reslurried in deionizedwater (100 mL) for 10 min. with stirring, and are again recovered bycentrifugation. The catalyst is dried in a vacuum oven at 50° C. and 30in. (Hg) to constant weight. This catalyst is identified as Catalyst A,and has the powder X-ray diffraction pattern shown in FIG. 4.

EXAMPLE 6 Epoxide Polymerizations: Rate Experiments--General Procedure

A one-liter stirred reactor is charged with polyoxypropylene triol (700mol. wt.) starter (70 g) and zinc hexacyanocobaltate catalyst (0.057 to0.143 g, 100-250 ppm level in finished polyol, see Table 2. The mixtureis stirred and heated to 105° C., and is stripped under vacuum to removetraces of water from the triol starter. The reactor is pressurized toabout 1 psi with nitrogen. Propylene oxide (10-11 g) is added to thereactor in one portion, and the reactor pressure is monitored carefully.Additional propylene oxide is not added until an accelerated pressuredrop occurs in the reactor; the pressure drop is evidence that thecatalyst has become activated. When catalyst activation is verified, theremaining propylene oxide (490 g) is added gradually over about 1-3 h ata constant pressure of 20-24 psi. After propylene oxide addition iscomplete, the mixture is held at 105° C. until a constant pressure isobserved. Residual unreacted monomer is then stripped under vacuum fromthe polyol product, and the polyol is cooled and recovered.

To determine reaction rate, a plot of PO consumption (g) vs. reactiontime (min) is prepared (see FIG. 1). The slope of the curve at itssteepest point is measured to find the reaction rate in grams of POconverted per minute. The intersection of this line and a horizontalline extended from the baseline of the curve is taken as the inductiontime (in minutes) required for the catalyst to become active. Theresults of reaction rates and induction times measured for variouscatalysts at 100-250 ppm catalyst levels appear in Tables 2 and 3.

EXAMPLE 7 Polyether Polyol Synthesis: Effect of Catalyst on PolyolUnsaturation, Catalyst Removal, and Polyol Quality

A two-gallon stirred reactor is charged with polyoxypropylene triol (700mol. wt.) starter (685 g) and zinc hexacyanocobaltate catalyst (1.63 g).The mixture is stirred and heated to 105° C., and is stripped undervacuum to remove traces of water from the triol starter. Propylene oxide(102 g) is fed to the reactor, initially under a vacuum of 30 in. (Hg),and the reactor pressure is monitored carefully. Additional propyleneoxide is not added until an accelerated pressure drop occurs in thereactor; the pressure drop is evidence that the catalyst has becomeactivated. When catalyst activation is verified, the remaining propyleneoxide (5713 g) is added gradually over about 2 h while maintaining areactor pressure less than 40 psi. After propylene oxide addition iscomplete, the mixture is held at 105° C. until a constant pressure isobserved. Residual unreacted monomer is then stripped under vacuum fromthe polyol product. The hot polyol product is filtered at 100° C.through a filter cartridge (0.45 to 1.2 microns) attached to the bottomof the reactor to remove the catalyst. Residual Zn and Co are quantifiedby X-ray analysis.

Polyether diols (from polypropylene glycol starter, 450 mol. wt.) andtriols are prepared as described above using zinc hexacyanocobaltatecatalysts made by conventional methods (stirring) and by the method ofthe invention (homogenization). The impact of the catalysts of theinvention on epoxide polymerization rate (Table 2), induction period(Table 3), polyol unsaturation (Table 4), catalyst removal (Table 5),and polyol quality (Table 6) are shown in the tables.

EXAMPLES 8-11 Preparation of Zinc Hexacyanocobaltate Catalyst:Tert-Butyl Alcohol Present During Formation of the DMC Compound

A round-bottom flask equipped with mechanical stirrer, addition funnel,and thermometer is charged with distilled water, potassiumhexacyanocobaltate, and tert-butyl alcohol (See Table 7 for amounts).The mixture is stirred until all of the potassium salt dissolves. Theresulting solution is heated to 30° C. To the stirred solution is addeda 50/50 (wt/wt) solution of zinc chloride in water over 50 min (seeTable 7). Stirring continues for another 30 min. at 30° C. The resultingwhite suspension is filtered under pressure at 30 psig. An 8.0 g portionof the filter cake is resuspended with vigorous stirring in a solutionof tert-butyl alcohol (110 g) and water (60 g). After all of the solidsare completely suspended in the wash solution, stirring continues for 30min. The mixture is filtered as described above. The entire filter cakeis resuspended in 99.5% tert-butyl alcohol (144 g), and is isolated asdescribed above. The filter cake is dried at 45° C. overnight undervacuum. The catalyst is used to prepare a polyoxypropylene triol havinga molecular weight of about 6000 and a hydroxyl number of about 28 mgKOH/g generally using the procedure of Example 7, but on a smaller scalewith a propoxylated glycerin starter triol (hydroxyl number 240 mgKOH/g) and a catalyst level of 250 ppm in the final polyol. Theunsaturations of the polyols appear in Table 7.

COMPARATIVE EXAMPLE 12 Preparation of Zinc Hexacyanocobaltate Catalyst:Tert-Butyl Alcohol Added After Formation of the DMC Compound

The procedure of Examples 8-11 is generally followed, but is modified asdescribed below. Tert-butyl alcohol is not added initially; the reactoris charged with water and potassium hexacyanocobaltate (see Table 7 foramounts). After the aqueous zinc chloride solution is added, thetert-butyl alcohol is added, and the mixture is stirred for 30 min. at30° C. The catalyst is then isolated, dried, and used to prepare apolyether triol as described previously (See Table 7).

The results of Examples 8-11 and Comparative Example 12 show the lowerpolyol unsaturations available from using a catalyst made by the processof the invention with tert-butyl alcohol initially present duringprecipitation of the catalyst.

EXAMPLES 13 and 14 Effect of Order of Addition of Reactant Solutions onCatalyst Activity Tert-Butyl Alcohol Added During Formation of the DMCCompound EXAMPLE 13

Solution 1 is prepared by dissolving zinc chloride (75 g) in tert-butylalcohol (50 mL) and distilled water (275 mL). Solution 2 is prepared bydissolving potassium hexacyanocobaltate (7.5 g) in distilled water (100mL). Solution 3 is prepared by mixing tert-butyl alcohol (2 mL) anddistilled water (200 mL).

Solution 2 is added to solution 1 over 30 min. with homogenization.Mixing by homogenization continues for an additional 10 min. A stir baris added. Solution 3 is added, and the mixture is slowly stirredmagnetically for 3 min. The mixture is filtered under pressure at 40psig. The filter cake is reslurried in tert-butyl alcohol (130 mL) anddistilled water (55 mL), and the mixture is homogenized for 10 min. Themixture is filtered as described before. The cake is reslurried in neattert-butyl alcohol (185 mL), and is homogenized for 10 min. The mixtureis filtered, and the cake is dried under vacuum at 60° C. Yield: 8.6 g.The catalyst is used to polymerize propylene oxide as described inExample 6. The rate of polymerization at 105° C. and 10 psig at 100 ppmcatalyst is 26.3 g PO/min.

EXAMPLE 14

Solution 1 is prepared by dissolving potassium hexacyanocobaltate (7.5g) in distilled water (300 mL) and tert-butyl alcohol (50 mL). Solution2 is prepared by dissolving zinc chloride (75 g) in distilled water (75mL). Solution 3 is prepared from tert-butyl alcohol (2 mL) and distilledwater (200 mL).

Solution 2 is added to solution 1 over 30 min. with homogenization.Mixing by homogenization continues for an additional 10 min. A stir baris added. Solution 3 is added, and the mixture is slowly stirredmagnetically for 3 min. The mixture is filtered under pressure at 40psig. The catalyst is isolated, washed, and dried as described inExample 13. The catalyst is used to polymerize propylene oxide asdescribed in Example 6. The rate of polymerization at 105° C. and 10psig at 100 ppm catalyst is 15.6 g PO/min.

The results from Examples 13 and 14 show the effect of reversing theorder of addition of reagents in a process of the invention. The resultsshow the unexpectedly higher catalyst activity available from a catalystmade by adding the metal cyanide salt solution to the metal saltsolution.

The preceding examples are meant only as illustrations. The scope of theinvention is defined by the claims.

                  TABLE 1                                                         ______________________________________                                        DMC Catalyst Characterization                                                                               Sur-                                                                          face                                                   X-Ray Diffraction Pattern                                                                            area.sup.4                                             (d-spacings, angstroms).sup.1                                                                        (m.sup.2 /                                      ID  Catalyst 5.07    4.82  3.76  3.59 2.54 2.28 g)                            ______________________________________                                        A   Cryst.   X       absent                                                                              absent                                                                              X    X    X    454                               Zn--Co.sup.2                                                              B   TBA      X       X     X     X    X    X    82                                stirred.sup.2                                                             C   IPA      X       absent                                                                              X     X    X    X    n.m.                              stirred.sup.2                                                             D   TBA      absent  X     X     ab-  ab-  ab-  14                                homog..sup.3                 sent sent sent                               E   IPA      absent  X     X     ab-  ab-  ab-  n.m.                              homog..sup.3                 sent sent sent                               ______________________________________                                         X = Xray diffraction line present; n.m. = not measured.                       Samples were analyzed by Xray diffraction using monochromatized               CuKα.sub.1 radiation (λ = 1.54059 Å). A Seimens D500         Kristalloflex diffractometer powered at 40 kV and 30 mA was operated in a     step scan mode of 0.02° 2θ with a counting time of 2             seconds/step. Divergence slits of 1° conjunction with monochromete     and detector apertures of 0.05° and 0.15° respectively. Eac     sample was run from 5° to 70° 2θ.                         .sup.1 Water of hydration can cause minor variations in measured              dspacings.                                                                    .sup.2 Comparative example.                                                   .sup.3 Catalyst of the invention.                                             .sup.4 Surface area is measured by nitrogen adsorption using the standard     BET method.                                                              

                  TABLE 2                                                         ______________________________________                                        Effect of Catalyst on Epoxide Polymerization Rate (105° C.)            ID  Catalyst   Cat. amt. (ppm)                                                                           Rate of polymerization (g/min)                     ______________________________________                                        F   glyme.sup.1,2                                                                            250         3.50                                                              130         1.78                                                              100         1.46                                               B   TBA stirred.sup.2                                                                        250         3.64                                                              130         2.50                                                              100         2.29                                               D   TBA homog..sup.3                                                                         250         10.5                                                              130         7.40                                                              100         3.84                                               C   IPA stirred.sup.2                                                                        250         <0.3                                               E   IPA homog..sup.3                                                                         250         1.70                                               ______________________________________                                         .sup.1 Catalyst F is prepared as described in U.S. Pat. No. 5,158,922.        .sup.2 Comparative example.                                                   .sup.3 Catalyst of the invention.                                        

                  TABLE 3                                                         ______________________________________                                        Effect of Catalyst on Induction Period (105° C.)                                         Catalyst                                                                      concentration                                               ID    Catalyst    (ppm)      Induction Time (min)                             ______________________________________                                        F     glyme.sup.1,2                                                                             100        230                                                                250        180                                              B     TBA stirred.sup.2                                                                         100        220                                                                130        180                                                                250        90                                               D     TBA homog..sup.3                                                                          100        140                                                                130        130                                                                250        85                                               ______________________________________                                         .sup.1 Catalyst F is prepared as described in U.S. Pat. No. 5,158,922.        .sup.2 Comparative example.                                                   .sup.3 Catalyst of the invention.                                        

                  TABLE 4                                                         ______________________________________                                        Effect of Catalyst on Polyol Unsaturation                                                     Polyol OH #        Polyol                                                     (mg KOH/g)         unsaturation                               ID  Catalyst    and functionality                                                                          Solvent                                                                             (meq/g)                                    ______________________________________                                        F   glyme.sup.1,2                                                                             54 (Triol)   none  0.016                                                      27 (Triol)   none  0.017                                                      15 (Triol)   none  0.019                                      B   TBA stirred.sup.2                                                                         35 (Triol)   none  0.011                                                      27 (Triol)   none  0.010                                                      14 (Triol)   none  0.011                                      D   TBA homog..sup.3                                                                          27 (Triol)   none  0.005                                                      56 (Diol)    none  0.004                                                      27 (Diol)    none  0.005                                                      14 (Diol)    none  0.004                                                      31 (Triol)   THF   0.003                                                      12 (Triol)   heptane                                                                             0.006                                      ______________________________________                                         .sup.1 Catalyst F is prepared as described in U.S. Pat. No. 5,158,922.        .sup.2 Comparative example.                                                   .sup.3 Catalyst of the invention.                                        

                  TABLE 5                                                         ______________________________________                                        Effect of Catalyst on Catalyst Removal                                                                            Residual                                          Polyol OH #                                                                             Filtration        catalyst                                          (mg KOH/g)                                                                              Temp.             (ppm)                                     ID  Catalyst  and functionality                                                                         (°C.)                                                                          Solvent                                                                             Zn   Co                               ______________________________________                                        F   glyme.sup.1,2                                                                           27 (Triol)  100     none  28   12                               B   TBA       25 (Triol)  100     none  6    3                                    stirred.sup.2                                                             D   TBA       25 (Triol)  100     none  5    <2                                   homog..sup.3                                                                            14 (Diol)   100     none  4    <2                                             29 (Diol)   100     none  3    <2                                             14 (Triol)  100     none  4    <2                                             27 (Triol)  25      heptane                                                                             3    <2                                             14 (Diol)   25      heptane                                                                             6    <2                               ______________________________________                                         .sup.1 Catalyst F is prepared as described in U.S. Pat. No. 5,158,922.        .sup.2 Comparative example.                                                   .sup.3 Catalyst of the invention.                                        

                  TABLE 6                                                         ______________________________________                                        Effect of Catalyst on Polyol Purity and Clarity                                            Low Mol. Wt.                                                                  Polyol Impurity                                                  ID  Catalyst (Wt. %, by GPC)                                                                            Appearance (25° C., after 3                  ______________________________________                                                                  weeks)                                              F   glyme     5-10        hazy                                                D   TBA      none detected                                                                              clear                                               ______________________________________                                    

                  TALBE 7                                                         ______________________________________                                        Preparation of DMC Catalysts with Tert-Butyl Alcohol Initially                Present and Unsaturations of Polyether Triols (28 OH#) Made                   from the Catalysts                                                                         Potassium                                                                     hexacyano-                Polyol                                 Ex.  Water   cobaltate tert-Butyl                                                                            Zinc chloride                                                                         unsaturation                           #    (g)     (g)       Alcohol (g)                                                                           (50%) (g)                                                                             (meq/g)                                ______________________________________                                        8    435     15        15      30      0.0027                                 9    302     7.4       39      152     0.0035                                 10   430     5.0       5.0     40      0.0032                                 11   393     15        15      121     0.0030                                 C12  264     24        24      192     0.0072                                 ______________________________________                                    

We claim:
 1. A method of making a double metal cyanide (DMC) complexcatalyst, said method comprising reacting aqueous solutions of a metalsalt and a metal cyanide salt in the presence of a tertiary alcoholcomplexing agent, wherein one or both of the reactant solutions containsthe complexing agent, and wherein the metal cyanide salt solution isadded to the metal salt solution.
 2. The method of claim 1 wherein theDMC complex catalyst is a zinc hexacyanocobaltate.
 3. The method ofclaim 1 wherein the tertiary alcohol complexing agent is tert-butylalcohol.